1. Field of the Invention
The invention relates in general to a semiconductor structure and a manufacturing process thereof, and more particularly to a metal oxide semiconductor (MOS) structure and a manufacturing process thereof.
2. Description of the Related Art
In the high voltage system, it is important for a metal oxide semiconductor (MOS) device having a high off-state breakdown voltage (off-Vbd) and a low on-state resistance (Ronsp), so that the MOS device can be operated under high voltage to allow a high current flowing between the drain and the source. Thus, the power consumption of the MOS device will be lowered. However, high off-state breakdown voltage and high on-state resistance generally come together, when the off-state breakdown voltage increases, the on-state resistance comparatively increases. Therefore, it does not tend to design a MOS device having an off-state breakdown voltage toward to maximum. It is an urgent problem to be resolved for industries to design MOS device having a high off-state breakdown voltage and a low on-state resistance.